Sea cucumber-inspired new plastic grows rigid to floppy when soaked in water

London, March 7 : Inspired by a peculiar characteristic of sea cucumbers' supple skin that enables them to become considerably stiffer and soften again within seconds, scientists have now created a polymer that can change dramatically from rigid to floppy when soaked in water.

American scientists behind this innovation - Stuart Rowan and Chris Weder of Case Western Reserve University at Cleveland in Ohio - say that, while sea cucumbers' skin can become more than 10 times stiffer as a defensive reaction to touch, the new material can soften by more than 2500 times.

"It's directly inspired by the sea cucumber," New Scientist magazine quoted Rowan as saying.

"We have the elastic polymer, so that's the mimic for the sea cucumber skin, and then we put in the cellulose whiskers. You can get these from paper pulp, but we got ours from another little sea creature called a tunicate," Rowan added.

The researchers say that simply soaking the transparent material in warm water for 15 minutes is all it takes to complete the transformation, and after drying out, it is identical to its original rigid state.

They also say that their material behaves differently to more common materials that go floppy in water like foam or cardboard, changes its properties more dramatically, and does not take on large amounts of water when soaked.

According to them, the material could be useful for electrodes implanted into the brain, such as for patients with Parkinson's disease or for brain control interfaces.

The researchers say that the rigid material could easily be inserted into brain tissues before softening into its floppy state, and thus it may help reduce the problems of inflammation that solid electrodes can cause.

They are now working on versions of the material that switch stiffness in response to a pulse of electricity.

"I think it is one of the most exciting recent opportunities in the design of new materials. It will open the door to applications in a number of different fields," says Craig Hawker of the University of California in Santa Barbara, US.

"One can imagine protective clothing for example, which is flexible and comfortable to wear, but becomes rigid and protective when necessary. This is essentially what sea cucumbers use this process for," Hawker says.

Robert Langer of Massachusetts Institute of Technology, US, adds: "Perhaps it could also be used as a stimuli responsive system for drug delivery."

A report describing the new material has been published in the journal Science.

ANI